The present invention relates to intrusion detection system in general, and specifically to fencing systems utilizing taut wires and detector devices to detect intrusion.
Numerous types of intrusion detection fences have been developed in order to successfully detect attempts of intruders to circumvent the system. Reference is now made to FIG. 1 which illustrate a typical prior art system such as U.S. Pat. No. 4,367,459 to Amir which consists of a fence having a plurality of trip wires 12 secured between two anchored posts 14 and a detector post 16 located between the anchored posts 14. A detecting device 18 such as a transducer is fixed to the intermediate detector post 16. Typically, the anchor posts 14 are located between 30 and 60 meters apart, that is the detector post 16 is approximately 15-30 meters away from an anchor post 14. The plurality of trip wires 12 are connected to a common actuator 20, which is supported by detector post 16. Any change in the lateral tension of wire 12 due to bending or cutting of the wire, for example, is xe2x80x98receivedxe2x80x99 by the common actuator 20 and transmitted to the transducer (detecting device 18).
The larger the distance between detector post 16 and anchor posts 14, the less sensitive the detection system. This is especially so in the vicinity of the anchor posts 14 further away from a common actuator 20, since as a result of the lateral movement of the wire deflection adjacent to the anchor post 14 is at a minimum near the common actuator.
In order to overcome these disadvantages, wire guiding posts 22 are placed between the detector posts 16 and between the anchor post 14 and the detector posts 16 to guide the wires 12 which slide through them without being held by them (the wires are not secured to the guiding post 22).
In a further variation as illustrated in FIG. 2, it is known to use one or more helical wire supports 24 between the common actuators 20 (in place of or in addition to wire guiding poles of FIG. 1). These helical wire supports 24 also act as sliding supports which translate the vertical motion of the wires, which have been bent or cut, into a lateral movement which can be sensed by the common actuator 20 and detected by the detecting device 18 connected to the common actuator 20.
However, these helical wire supports 24 (as shown in FIG. 2) or wire guiding posts 22 (as shown in FIG. 1) have the disadvantage that they can be easily mechanically cut, broken or removed by the intruder, actions which may not trigger the alarm. Thus, if an intruder has enough time, the removing or cutting of the helical wire cases the fence to lose its sensitivity. Thereafter, the intruder can, in some situations, move the taut wires apart without triggering the detecting device 18.
U.S. Pat. No. 4,829,287 to Kerr, schematically illustrated in FIG. 3 to which reference is now made, utilizes a plurality of detector posts 30 between anchor posts (not shown) and a plurality of sensors 32 which are mounted on each detector post 30. Each of the parallel taut wires 34, anchored to the anchor posts, engage a single sensor. Between horizontally consecutive sensors, wire guiding devices comprising a rod and helical coil support members 36 (similar to FIG. 2) are placed to guide the taut wires 34, keep them apart and translate the bending movement of the wire into a lateral motion through the helical coil supports.
Intrusion detection systems having a sensor fitted to each taut wire are much more expensive, since they require a sensor for each strand of wire, and consequently also require a great deal more maintenance. Eventually, the sensor parts of the taut wire system which are relatively costly and the most vulnerable parts of the system lose their sensitivity especially if not properly maintained. Therefore, these xe2x80x9csensor for each wirexe2x80x9d type systems are much more expensive in comparison to the xe2x80x9ccommon actuatorxe2x80x9d type of fences mentioned above.
While the xe2x80x9ccommon actuatorxe2x80x9d type fences are less expensive are generally less sensitive especially when the intruder removes or breaks the helical or guiding posts and thereby reducing the fence""s sensitivity and causing the fence to deteriorate and become less effective.
It is an object of the present invention to provide an improved intrusion detection fence utilizing a plurality of tensioned taut wires, which overcomes the limitations and disadvantages of prior art systems.
It is a further object of the present invention to improve the sensitivity of the system by reducing the opportunity for intrusion even when the intruder tries to reduce its sensitivity by removing or braking one or more of the guiding posts or helical supports. In the preferred embodiment, the intrusion detection system includes a plurality of active sensor devices each connected to a common actuator. The active sensor devices are placed between anchor posts which tautly restrain the taut wires.
There is therefore provided, in accordance with a preferred embodiment of the present invention, an intrusion detection fence, which includes a plurality of trip wires secured between a pair of anchor posts, a plurality of detector posts anchored in the ground, located between the anchor posts, at least one actuator attached to each of the detector posts, the actuator also being coupled to each of the plurality of trip wires; and a detecting device attached to the actuator and secured to each of the detector posts. The deflection or cutting of any of the plurality of trip wires activates at least one of the detecting devices adjacent to the activated trip wires.
Furthermore, in accordance with a preferred embodiment of the present invention, deflection of any of the plurality of trip wires activates each of the detecting devices either side of the activated trip wires.
Furthermore, in accordance with a preferred embodiment of the present invention, the actuator is an actuating wire tensioned between the ends of the detector post. The actuator is an actuator bar or flange.
Additionally, in accordance with a preferred embodiment of the present invention, the fence further includes a passive wire attached to each of the detecting device, the passive wire being parallel to the actuator wire.
In addition, in accordance with a preferred embodiment of the present invention, The detecting device is housed within a central leg of a generally xe2x80x9cIxe2x80x9d shaped housing, the housing further includes a bottom leg and a top leg attached to the central leg. The housing further includes a pair of clamps attached to the top leg for clamping common actuator wire and passive wire to the detecting device.
In addition there is also provided, in accordance with a preferred embodiment of the present invention, an intrusion detection system which includes a fence having a plurality of trip wires secured between a pair of anchor posts, a plurality of detector posts anchored in the ground, located between the anchor posts, at least one actuator attached to each of the detector posts, the actuator also being coupled to each of the plurality of trip wires, a detecting device attached to the at least one actuator and secured to each of the detector posts: and a control center coupled to each of the detecting devices. The control center includes a processor for determining and indicating the location of detecting device activated by the deflection of any of the trip wires.
In a second embodiment, in accordance with a preferred embodiment of the present invention, the system and fence further include a plurality of guiding posts, each guiding post being located between each pair of detecting posts or between a anchor post and a detecting post. The actuating wire is tensioned between the top of one of the guiding posts and the bottom of the adjacent guiding post. Alternatively, the actuating wire is tensioned between one end of one of the guiding posts and the end of one of the anchor posts.
Furthermore, in accordance with a preferred embodiment of the present invention, the fence and system further include a second detecting device attached to at least one of the pair of anchor posts.
Furthermore, in accordance with a preferred embodiment of the present invention, the actuating wire is further tensioned between the top and bottom ends of one of said pair of anchor posts and attached to the second detecting device. Alternatively, the actuating wire is further tensioned between the top or bottom end of an anchor post and attached to the second detecting device.
Furthermore, in accordance with a preferred embodiment of the present invention, the fence and system further includes a second actuating wire attached to and tensioned between the top and bottom ends of the anchor post and attached to the second detecting device.
Additionally, in accordance with a preferred embodiment of the present invention, the fence and system further includes second and third actuating wires. The second actuating wire is tensioned between one end of one of the pair of anchor posts and the third actuating wire is tensioned between the other end of the anchor post.
Furthermore, in accordance with a preferred embodiment of the present invention, the detecting devices are torque sensitive devices.